Self-releasing machine drive



Patented Mar. 16, 1943 ED: ST

Ladislav Boor, New Canaan, and Chesman Henry Bourdelais, Stamford,

American Cyanamid Company,-

Conn., assignorsg to New York,

N.`Y., a corporation of Maine Application March 4, 1941i, serial No.381,742 1v claim. (ci. 265-12) ''his invention relates to al self-releasing clutch, and more particularly jto; an improved machine driveembodying a clutch which releases automatically upon removal of the loadbeing driven.

Many problems have, arisen in industry and in the laboratory due to thelack ofv a machine drive mechanism which is ada-pted to transmitconsiderable power when loaded but which will stop at the instant theload is removed. An outstanding eld in which such problems frequentlyarise is the eld of testing materials where accurate determinationsdepend Aon the speed with which the drive mechanism becomes disconnectedfrom the testing machine after the test material has broken, i, e.,after the load has been removed from the driving mechanism.

Applicants have found that the above problems may be solved by applyingthe improved driving mechanism of the present invention with itsautomatically releasing clutch, to a testing machine. The clutchautomatically disengages at the instant of fracture of the materialbeing tested and this, of course, results in a more accuratedetermination of the strength of the material.

While the improved machinedrive of the present invention may be utilizedin any machine, applicants have found it lespecially adapted for usewith the Dynstat testing machine. This machine, which is manufactured bythe firm Louis Schopper, Leipzig, has found wide application in thedetermination of the transverse strength of such materials as syntheticresins, plastics, hard Wood, hard rubber, glass, composition board, etc.In fact, it may be used to test any material which breaks within therange of load of the machine. Replacement of the old conventional handcrank drive of a Dynstat testing machine by a machine drive, preferablymotor driven, embodying the self -releasing clutch of the presentinvention provides a more uniform rate of stressing and produces moreaccurate determinations. Uniformity of resultI is further increasedsince the drive is independent of the load. Handcranking against a heavyload is at best a jerky proposition and non-uniform, inaccuratedeterminations necessarily result. The disadvantage is completelyeliminated by the machine drive of the present invention.

The self-releasing clutch will be described with specific reference toits embodiment in the drive of a Dynstat testing machine, but it shouldbe understood that applicants do not intend to limit their invention tothat specific embodiment. Referring to the drawing,

Fig. 1 is a front elevation of the Dynstat testing machine havingV adrive mechanism which includes the automatically releasing clutch of thepresent invention;

' Fig. 2 is a section 'Fig'.i; and

Fig. 3 is a detail perspective view of the clutch members.

The drive mechanism is connected to a conventional Dynstat testingmachine by means of the shaft I which is supported at 2 by a bracket 3.The upper clutch member 4 with downwardly engaging pins 5 is fixed tothe shaft I by means of pin 6. Lower clutch member 1 with upwardlyextending lugs 8 is provided ill, thus providing a circumferentialgroove II for the purpose hereinafter described, and is keyed at I2 (seeFig. 3) to shaft I3, which is driven by motor I4, in such a way that itis free to slide vertically on the shaft but is incapable of any rotarymotion independent of the shaft. A forked lever I5, hich is pivoted atI5, is joined to lower clutch member 1 by means oi'rroller pins I'I (seeFig. 2) which are set in the forked end of the lever and extend into thecircumferential groove II referred to above. Such an arrangement makesit possible for lower clutch member 'I to rotate freely with shaft I3,but any vertical movement of lower clutch member 'I along shaft I3 isaccompanied 1`v a corresponding displacement of lever I5. The forceexerted by spring I8 on lever I5 tends to `disengage lower clutch member1 and the amount of this force may be varied by means of the adjustingscrew I9.

Fig. 1 shows a Dynstat testing machine set for determination of thetransverse strength of a sample by means of bending tests andaccordingly the operation of Y applicants device will be described indetail in connection with such a determination. 'Ihe sample to be testedis placed at 20 between the arm 2 I, which is fixed to inner plate 22,and pendulum 23 of the conventional Dynstat. After the motor I4 isstarted up, thus setting in motion the shaft I3 and lower clutch member1 in the direction indicated by the arrow on the drawing, the lever I5is depressed, the lower clutch member 'I is moved upward on the shaft I3and becomes engaged with the upper clutch member 4. Lower clutch member'I is prevented rom dropping out of engagement with upper clutch member4 s o long as the sum of the forces exerted on the lever I5 by thespring I8 and by gravity is less than the frictional force between pins5 and lugs 8 which frictional force varies directly as the load .onshaft I. Shaft I,

taken along the line 2-2 of with fianges 9 and

